Bridget's Yo-Yo

Making a Functional Yo-Yo

This post is going to go over my process for 3D modelling a functional 7" Yo-Yo. If you just want the functional finished prop for your own use, it's freely available here, but I'm detailing the process for transparency and because the techniques within are applicable elsewhere.

While this post describes a Yo-Yo, ideally it should be helpful for cleanly taking a prop concept from idea to reality.

Fusion was the software used in the design. Some of the operations below may be applicable in other software, but in general I would like to note that CAD (Computer-aided design) software, like Fusion, is preferable to 3D modelling software (like Blender, Maya) when designing things meant to exist in the real world. For a quick simplification: CAD creates an optimized end model from a series of well-defined operations, whereas 3D modelling software manipulates polygons, where end results can be very blocky if not smoothed.

When designing a functional prop, it's important to keep your mechanisms in mind. While of course I modeled to match the appearance of the in-game reference, knowing that I wanted my yo-yo to actually spin and retract, I made the internals such that they would snugly nest a real yo-yo inside to act as a driver.

While it would not be impossible to 3D print the remaining yo-yo parts instead of using a driver, parts like screws and screw-holes are impractical to print due to risk of wear. More importantly, the internals are not visible- there's no reason to re-invent a yo-yo if you don't need to, don't make extra work for yourself.

A quick note before diving into the step-by-step process, Fusion features a timeline at the bottom of the screen. Any operation you do is added to this list and can be edited, suppressed, deleted, or rearranged.

This is helpful, because any change to this timeline will ripple. For example, if you made a six inch cylinder, then later cut into it, you could edit the cylinder to be seven inches, and Fusion would apply the same cuts to the new cylinder without making you start over.

While the changes in the example were right next to each other, this still applies even if there are dozens of operations after a timeline change- with the caveat that some operations can break and be automatically suppressed if a change removed something they referenced.

To start off, I went with the most basic shape to refine later, I created a cylinder with the dimensions I wanted for the full yo-yo (7" diameter, 2" tall) and cut a smaller cylinder out of it with the width of my real yo-yo (2.3" diameter)

Copying the created body, I now have my two halves to manipulate

Going forward, the sketch tool will be important. Sketches let you define geometric shapes that can be extruded into their own bodies, or used to manipulate existing bodies.

Here with just two regular hexagons of different sizes perpendicular to each other, I'm able to evenly place 12 circles (at each hexagon point) which will later be used for the bullet chambers and the notches on the outside of the yo-yo.

This base sketch will be used throughout the build, along with a couple of other sketches that include more detail.

Notably, you can see that the complex shape in the highlighted area will eventually become the black area in the finished yo-yo.

First, the inner six circles are cut a short depth into the tops of both halves of the yo-yo to create bullet chambers.

Then, the outer six circles are extruded into cylinder, and "combine->cut" is used to cut those cylinders out of the main body.

Note that the height of the cylinders was made slightly shorter than the yo-yo top, as the notches don't cut all the way through in-game.

So far, the yo-yo has had exclusively sharp edges. To give a more natural feel, I am going to bevel my edges using the Chamfer tool. Selecting the edge of the circle and giving 0.2 inches of chamfer creates a straight slope around the yo-yo.

The Fillet tool can be used for more rounded transitions, and more complicated shapes with either tool if you select multiple edges or faces, but throughout this design, I generally only needed to select a single edge or a single face.

Using the same techniques above, I extruded more cylinders from my base sketch and beveled them using chamfer to fully define all six bullets on both sides of the yo-yo.

In general, I applied chamfers to most edges around the whole design to keep it rounded. 

Each of her bullets is engraved. In the sketch tool, you can add text, and selecting "fit to path" and selecting the inner circle, I was able to wrap my text evenly around the bullet.

The emboss tool can then be used to cut that sketch text into the bullet. Note that using the proper emboss tool was much cleaner in my experience than trying to extrude/cut the sketch text, which leads to complicated geometry and a messy timeline. (As the intermediate shapes like the two circles inside the 8 become tracked separately with extrude)

Emboss was also used for some small detail text on the outside ring of the yo-yo.

Using more cylinders for extruding and cutting, I created a small hole with a lip inside each half, the measurement of the groove matching the outer indentation of my yo-yo so it nests snugly.

The hole being fully open inside of that circle also means that the spinner in the yo-yo (the bit on the outside where you can do tricks spinning the yo-yo on your finger like a basketball) is exposed and accessible so that those tricks are still possible.

Lastly, on one of the holes, I added teeth. I did this by sketching a quick trapezoid and using the sketch tool "circular pattern" to make 6 evenly spaced copies of it around a circle, which I then extruded and beveled.

Once printed, I made sure to thoroughly sand the print to get it smooth and ready for painting! If you aren't familiar with this process, which is out of scope of this log, I'll cede to Lutavia Cosplay's panel on prop finishing.

Reminder to wear proper eye and respiratory protection when sanding and painting.

I painted with spray paint, using masking tape to cover previous colors on lower layers as I went.

And with all that completed, the Yo-Yo is now fully functional!

It can be seen in motion in the clip to the right.

Thanks for following along!